Milo g



(No Model.)

M. G. KELLOGG.

MULTIPLE SWITGHBOARD.

Patented Oct. 26,1897.

with STATES FFICE.

MILO G. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO Tll E KELLOGGSlVI'lClllKOARD AND SUPPLY COMPANY, OF SAME PLACE.

MU LTIPLE SWITCHBOARD.

SPECIFICATION forming part of Letters Patent No. 592,356, dated October26, 1897.

I Application filed January 8, 1890, Serial No. 336,261. (No model.) i

To aZZ whom it may concern.-

Be it known that I, MILO G. KELLOGG, of Chicago, in the county of Cookand State of Illinois, temporarily residing at Stuttgart, in the Empireof Germany, have invented cer' tain new and useful Improvements inMultiple Switchboards for Telephone-Exchanges, of which the following isa full, clear, concise, and exact description, reference being had tothe accompanying drawings, forming a part of this specification.

My invention relates to telephone-exchange systems in which the linesare metallic-circuit lines; and it consists in a system of testing suchlines which I shall describe and claim.

I place as manyboards in the central office as are found necessary ordesirable in order to properly answer the calls and make the necessaryconnections and disconnections. On each board is a spring-jack orsimilar switch for each line. Each switch has a contactspring and acontact-piece insulated from the spring, except by the circuitconnections, and is adapted to receive a loop-switch plug and, when aplug is inserted, to connect the two contact-pieces of the plug withsaid spring and said contact-pieces, respectively.

In the accompanying drawings,illustrating my invention, Figures 1 and 1represent sections of two multiple switchboards of the exchange to whichthe same lines are connected. Fig. 2 shows a diagram of the boards,withthe line connections and apparatus necessary to illustrate my invention.Fig. 3 shows an operators cord system to be used with the boards. Fig.4c shows an operators test system. Fig. 5 shows a subscribefsstationapparatus.

In the drawings like parts and apparatus are indicated by the sameletters and figures of reference.

G in each case represents a ground connec' tion.

In Fig. 2, A is a sectional view of the switchboard shown in Fig. 1, andA is a sectional view of the switchboard shown in Fig. 1 each asindicated by the line (Z c.

In Fig. 2, g 9 represent the springs of the switches and j the insulatedcontact-pieees pieces are mounted, as shown, and through the fronts ofwhich are the holes Z Z. The insulated contact-piecesjj of the switchesare so placed that a test-plug or similar device may readily be appliedto them.

W and X are calling-annunciators, one for each of the lines shown.

The circuit of a line is as follows and as shown: One side or branch ofthe line is connected with all the contact-pieces j j of its switches011 the boards. The other branch of the line is connected with all thecontactsprings g g of its switches 011 the different boards and throughthe line-annunciator to the ground.

In the operators cord system shown in Fig. 3, D D are the loop-switchplugs. m m are the two contact-pieces of each plug. These contact-piecespass to the bottom of the plughandles, as shown, and are adapted to restnormally (or when not in use) on the metal plate 0, which then connectsthe two contactpieces of the plug together. Y is a looping-in switch forthe pair of cords shown. '0 is the clearing-out annunciator for the pairof cords. t is the operators telephone, and B is her calling generatoror battery. The circuits are substantially as shown. 7

Only one pair of plugs and cords, with their apparatus, are shown. Otherpairs, as required, may be added to the system in a way which will beapparent to those skilled in the art.

In the subscribers test system shown in Fig. 4, T is the test-plug,connected with a flexible cord and adapted to be brought for testinginto connection with any contact-piece j at its board. S is the testreceiving instrument, and B is a test-battery. The parts are connectedtogether and to the ground substantially as shown.

Each operator has a cord system and a test system, and they areconveniently placed and mounted for her work.

In the subscribers station apparatus shown in Fig. 5, 1 is thetelephone-switch. 2 is the calling-generator. 3 is the signal-receivingbell. I is the subscribers telephone. 5 is the secondary, and G is theprimary, of the induction-coil. 7 is the transmitter. Sis thetransmitter-battery. 9isacondenser. These parts may be of usual forms ofapparatus and are connected as shown or in other ways so as to performpractically the operations required and the operations hereinafterdescribed. The generator, however, is modified and is as shown. When itis not in operation, the subscribers line is open to the ground at hisstation and is on'closed circuit, the two sides of the line being closedat the contacts at 0. While it is being operated the spring 42 passesout of contact with 0 and into contact with p and the line isautomatically connected with the ground, with the armature-coil betweensaid connection and the connection of the line to the ground at. thecentral office.

In the normal condition the armature of the generator is shunted thus:One side of the line is connected with the generator-frame at q, andspringnis connected with the frame andwith one terminal of thearmature-coil. The other terminal of the armature is connected with acontact on the shaft upon which the finger r bears, the fin gerbeingconnected with the other side of the line through the J bell andcondenser when the telephone is on its switch.

When a subscriber operates his generator to send in a call, his line isautomatically connected to theground, with his armature-coil between theconnection and the central-office ground connection of the line, and thelineannunciator will be operated, indicating his call.

The connections of the subscribers-station apparatus and switch are suchthat when the subscribers telephone is on its switch thesignal-receiving bell and the condenser are in the circuit of the lineand the telephone and the secondary of the induction-coil are shunted bya wire 00 of small resistance, so as to be practically out of thecircuit. When the telephone is off the switch, the telephone and thesecondary of the induction-coil are in the circuit and the signal-belland condenser are practically out of the circuit, being shunted by wirey. The resistance of the telephone and secondary of the induction-coilcombined aggregate, in wellconstructed apparatus, about four hundredohms and the resistance of the signal-bell amounts to about one hundredohms. The resistance of the condenser is such that when the telephone isin its normal position on its switch the line is practically open to thecurrent from any test-battery which is closed with it. However, thecircuit is then such that this current of a magneto-generator sent overit will operate the signal-bell. I utilize this difference in resistancein the operation of the calling and test system, as willhereinafte-rappear.

WVhen an operator receives a call,she places one of a pair of herswitch-plugs in the switch of the line, the contact-piece m being'inconnection with the spring 9, and there is a complete circuit of theline established through the two branches of the line, the twocontact-pieces of the plug used, the pairs of the circuit.

conductors of the cords, the two contactpieces of the other plug of thepair, and the metal piece which then connects them together, and theoperator can, by moving the switch Y connect her telephone with thecircuit and find out what line is wanted. When on testing the linewanted she finds it to be the branches of the two lines connected withthe springs g, and this groundis between the two ground connections inwhich are the two line-annunciators. When two lines are connectedtogether, the operator may, by operating the switch Y of the pair ofcords used, thus connect at will either her telephone, hercalling-generator,or the clearing-out annunciator into the circuitbetween the two branches of the lines connected with the contact-piecesj.

It. will be seen that when the switch-plugs are placed into the switchesof two lines, as described, one branch of the circuit is grounded at thecentral office by two circuits through the line-annunciators of the twolines and that they are shunted by the circuit of the clearing-outannunciator. The latter circuit is of much smaller resistance, and thelineannunciators of high resistance are thereby shunted by a circuit ofso small resistance that any signal sent over the lines will not operatethe line-annunciators, and when two I lines are connected in metalliccircuit, as described, both line-annunciators are shunted (when thegeneratoris operated and grounded 1 at either subscribers station)through the grounded cord connection. 1

j When an operator receives acall on a line assigned to her, she placesone of the switchplugs of a pair in the switch of the line, and, movingthe levers of the looping-in switch, connects her telephone into thecircuit and finds out what line is wanted. She then. tests the linewanted, and if she finds it is not busy she places the other plug of thepair in its switch. She then moves the levers of the switch so that thecallinggenerator is in the circuit and a signal-current is sent over theThe callinggenerator should be of such strength that it will operate thesubscribers signal-bell through the resistance of .the two lines,including the condenser in circuit while the subscribers telephone isnot switched for use. The calling-generators generally used by operatorsare of such strength as to accomplish this. \Vhen the operator has senta calling-current to the cir- IIO generator of either subscriber isoperated is of such strength that the clearing-out annunciator will beoperated, but the line-annunciators in the ground branches of the lineswill not be operated.

The operators test receiving instrument and battery should be soconstructed and related that when they are closed to the contactpiece jof the switch of any line and the subscribers telephone is not switchedfor use and the condenser is therefore in the circuit the instrumentwill not sound and that when the subscribers telephoneis switched foruse and the condenser is not in the circuit the instrument will sound.

This construction and relation between the test receiving instrument andbattery can be readily obtained. They depend on the fact that anelectromagnet may be readily constructed so as to operate when a batteryand a certain resistance are in circuit with it and not to operate whenthe resistance is very much greater. This operation can be made todepend on the style of the magnet,the number of convolutions of itscoil, the size of the battery, and the adjustment of the retractilespring.

When an operator desires to test any line to determine whether it isfree to be switched to, she places her test-plug on the contactpiece jof the line at her board. The testeircuit is from the ground through hertest receiving instrument and battery to the line and through thecircuit of the line back to its ground at the central ofliee. If thesubscribers telephone is not switched for use,his condenser is in thiscircuit and the test receiving instrument will not sound because thecircuit is practically open to the test-battery. If, however, thesubscribers telephone is switched for use, there is a circuit throughhis station apparatus independent of the condenser and enough currentpasses through the test receiving instrument to operate it. The operatorcan therefore determine whether or not the line is free to be connectedwith.

In this system only two contact-points are required for each line ateach board.

I have described herein a system of clearing out in which theline-annunciators are shunted by a circuit connection containing aclearing-out annunciator. I do not, however, claim such subject-matterherein, as it is claimed in another pending application filed by me.

I claim as my invention and desire to secure by Letters Patent- 1. In atelephone-exchange system, a metallic-circuit telephone-line normallyopen at one end at the central office and permanently grounded at itsother end at the central office and normally grounded there only, incombination with a condenser at the subscribers station and switchingapparatus by which the condenser is switched into the circuit of hisline while his telephone is not switched for use and out of the circuitwhile the telephone is switched for use, and a test wire or circuitcontaining a test receiving instrument and battery grounded at one endand connected on its other side to a test plug or device adapted, at thewill of the operator, to be brought into connection with the normallyopen end of the line, substantially as set forth.

2. In a telephone exchange system, two or more multiple switchboards atthe central office, and metallic-circuit lines connected to them, eachline being normally open at one end and connected to each board and atits other end permanently grounded and connected to each board, andnormally grounded there only, in combination with a condenser at thesubscribers station and switching apparatus by which the condenser isswitched into the circuit of his line while his telephone is notswitched for use and out of the circuit while the telephone is switchedfor use, and a test wire or circuit containing a test receivinginstrument and battery grounded at one end, and connected on its otherend to a test plug ordevice adapted, at the will of the operator, to bebrought into connection with the normally open end of any line,substantially as set forth.

3. In a telephone exchange system, metallic-circ nit lines, multipleswitchboards for the same and switches, one switch on each board foreach line, each switch having two contactpoints, one of which ispermanently connected to one side of the line and is permanentlyconnected with the ground and the other of which is connected to theother side of the line, in combination with a condenser at thesubscribers station and switching apparatus by which the condenser isswitched into the circuit of his line while his telephone is notswitched for use and out of the circuit while the telephone is switchedfor use, test receiving instruments, one at each board, each instrumentgrounded on one side and connected on its other side to a test plug ordevice adapted, at the will of the operator, to be brought fortestinginto connection with anyof said second-mentioned contact-pointsof the switches at its, board, and battery in the test-circuitestablished on testing, substantially as set forth.

4. In a telephone-exchange system, a metallic-circuit telephone-linenormally open at one end at the central oflice and permanently groundedat its other end at the central office and normally grounded there only,in combination with a condenser at the subscribers station and switchingapparatus by which the condenser is switched into the circuit of hisline while his telephone is not switched for use and out of the circuitwhile the telephone is switched for use, a test wire or circuitcontainin g a test receiving instrument grounded at one end andconnected on its other side to a test plug or device adapted, at thewill of the operator, to be brought into connection with the normallyopen end of the line, and battery in the test-circuit normallyestablished on testing, substantially as set forth.

5. In a telephone-exchange system, a metallic-circuit telephone-linenormally open at one end at the central office and grounded at its otherend at the central office when the line isswitched for conversation andnormally grounded there only, in combination with a condenser at thesubscribers station and switching apparatus by which the condenser isswitched into. the circuit of his line while his telephone is notswitched for use and out of the circuit while the telephone is switchedfor use, and a test wire or circuit containing a test receivinginstrument and battery grounded at one end and connected on its otherside to atest plug or device adapted, at the will of the operator, to bebrought into connection with the normally open end of the line,substantially as set forth.

6. In a telephone-exchange system, a me- Y tallic-circuit telephone-linenormally open at one end at the central office and grounded at its otherend at the central oflice when the line is switched for conversation andnormally grounded there only, in combination with a condenser at thesubscribers station and switching apparatus by which the condenser isswitched into the circuit of his line while his telephone is notswitched for use and out of the circuit while the telephone is switchedfor use, a test wire or circuit containing a test receiving instrumentgrounded at one end and connected on its other side to a test plug ordevice adapted, at the will of the operator,

to be brought into connection with the normally open end of the line,and battery in the test-circuit normally established on testing,substantially as set forth.

In witness whereof I hereunto subscribe my name this 20th day ofDecember, 1889.

MILO G. KELLOGG. \Vitnesses:

EMIL ABENHEIM, MARGARETHA RIEHL.

